The coated abrasive products industry is continuously seeking new and better means to satisfy the continuing demand for fast, efficient and durable abrading products.
By coated abrasives it is generally meant to describe those products having abrasive granules adhered to a supporting backing which can be used to abrade or otherwise wear down the surface of an article on which they are worked and which typically are generically referred to as sandpaper. The support backing may be rigid, but generally is flexible and typically comprises a fibrous material such as cloth or paper. The abrasive granules generally comprise a particulate material typically having sharp cutting edges and the capability of abrading the material from which the article to be abraded is manufactured. The granules typically are adhered to the support backing by an adhesive binder material and the like.
A continuing problem with coated abrasives is that they are typically used during a manufacturing process to abrade the surface of products comprised of soft materials such as aluminum, wood, plastic and the like wherein the abraded material from the product, and/or softened material from the binder or support backing, undesirably adheres around and about the granules in such manner as to build-up, clog or otherwise reduce the effective abrading surface of the coated abrasive and accordingly the efficiency of the abrading process.
Multiple factors contribute to such build-up or clogging of adhering materials about the abrasive granules and the resulting loss in efficiency of the coated abrasive. Some primary factors include static charge build-up on the coated abrasive which attracts abraded particles and retains them to the coated abrasive; overheating of the coated abrasive which may cause material from the abraded article to burn or otherwise accumulate around and about the cutting surfaces of the granules; overheating of the binder or support backing which may cause them to soften; and, loading build-up which comprises the natural adhering tendency of the material, or components thereof, being abraded to otherwise accumulate about the granules of the coated abrasive.
Thus, when the article to be abraded or sanded is comprised of a material such as wood, particularly wood which may have been filled and/or sealed, abrading the article with a conventional coated abrasive typically results in the clogging of the coated abrasive within a relatively short period of time due to the adhering of natural lignins, the sealer or filler compositions typically caused by the heat generated during the abrading process. Where the abrading process is by machine sanding or abrading, such as by continuous belt, disk sanding techniques and the like, a coated abrasive can become more rapidly clogged. In such circumstance, the machine abrading process not only becomes inefficient but there is increased difficulty in controlling the flow of machine abraded particulate matter into collectors. Since the collection of abraded particulate matter is important to control as it may create environmental concerns, the problem extends itself beyond manufacturing efficiencies. Hence, the machine abrading of products comprised of materials such as wood can require premature changing of the coated abrasive belts, disks and the like to satisfy environmental regulations relating to the collection of dust particles as well as manufacturing efficiencies. The result is increased material and labor cost to the manufacturer.
Various means have been devised to reduce the incidence of build-up or clogging on coated abrasives. Chemical additives, generically referred to as "sanding aids", have been incorporated in some sealing and filling compositions for application to materials such as wood, which indeed reduce the incidence of clogging of the coated abrasive. Invariably however, since such aids are applied directly to the wood, they are found to detract from the natural beauty of the finished product. Because of such problem other means have been proposed for use which avoid using materials such as sanding aids that are applied to the article to be abraded.
U.S. Pat. No. 2,768,886 describes the application of metallic soaps to the coated abrasive for the reduction of clogging. Such application does appear to decrease the incidence of clogging and is widely used in the industry, but is considered less efficient than desired.
U.S. Pat. No. 4,396,403, discloses the incorporating of phosphoric acids, partial esters of such acids, amine salts of such acids, quaternary ammonium salts and the like to the size coating of coated abrasives to achieve the loading resistance attained by the use of metal stearates. Such process is also used in the industry but is generally considered less effective than desired.
An object of this invention is to provide a convenient means to improve resistance to static build-up on a coated abrasive.
Another object of the invention is to provide a convenient means to improve resistance to loading build-up on a coated abrasive.
Still another object of the invention is to provide a coated abrasive having improved anti-static and improved anti-loading characteristics, particularly for machine abrading applications.
These and other objects of the invention will become apparent from the following.